Because of its transparency in the ultraviolet (248 nm) and deep ultraviolet (193 nm) ranges, silica glass is used extensively in the semiconductor industry as the lens material in stepper and stepper/scanner machines that use pulsed excimer lasers for transferring a mask pattern (at the top of the lens barrel) to a semiconducting wafer (at the bottom of the lens barrel). Consequently, the glass is exposed to high intensity, short wavelength radiation that can affect the refractive index and the transmission of the glass, both of which can affect image quality and wafer throughput. Controlling these dynamic processes is critical to maintaining stepper life, which is required to be many years, translating to hundreds of billions of pulses of laser radiation. A decrease in glass transmission, also referred to as induced absorption (IA), is frequently observed and typically increases linearly with the number of laser pulses, darkening the lens. Such IA behavior can potentially limit the lifetime of a stepper.